Abstract: Infections are common following surgery. It is critically important to identify infections quickly to avoid complications including readmission, implant failure or sepsis. Early detection allows time for cultures to be run and simple antibiotics to be effective. The Centers for Medicare & Medicaid Services recognize the serious nature of the problem and in 2015 started imposing significant penalties for surgical readmissions. In addition, early treatment enhances the probability that surgical implants and prosthetics remain viable because they usually have to be removed or replaced if infection takes hold. Inflammation is the earliest physiologic marker of infection, but it has many sources, and local inflammation is necessary for normal wound healing. Surgical site infection, however, may be distinguishable from normal wound healing by monitoring the character and time course of local inflammation at the surgical site. Inflammation from wound healing and low levels of bacterial infection begins within hours and abates completely within a few days after surgery, when the proliferative phase of wound healing begins. Inflammation from infection increases monotonically and can reach far higher levels than normal healing. So we believe that infection can be identified early by precisely tracking two local markers of inflammation: cytokine IL-6 and local temperature. We propose to use novel magnetic nanoparticle probes to compare changes in the local concentration of IL-6 and temperature for normal healing vs. infection. We hypothesize that measuring the local level of these inflammatory markers over time will aid detection of surgical infection. This novel technology may lead to an inexpensive, simple, point of care measurement system for early detection and treatment of surgical infections.